1. Field of the Invention
The present invention relates generally to apparatuses and methods for transporting and metering particulate material with improved drive force, and in particular embodiments, to such apparatuses and methods which can be used to both transport and meter solid material of a great range of sizes under both ambient conditions and against pressure.
2. Description of Related Art
A wide variety of equipment has been used to either transport or meter particulate material (such as, but not limited to, coal, other mined materials, dry food products, other dry goods handled in solid, particle form). Such transport equipment includes conveyor belts, rotary valves, lock hoppers, screw-type feeders, etc. Exemplary measurement or metering devices include weigh belts, volumetric hoppers and the like. In order to provide both transport and metering of particulate material, it was typically necessary to use or combine both types of devices into a system.
However, some of applicant's prior pump devices were provided with the capability of both transporting and metering particulate material. Examples of such prior designs include the rotary disk type pumps discussed in the following U.S. patents, each of which is assigned or licensed to the assignee of present invention and each of which is incorporated herein by reference: U.S. Pat. No. 4,516,674 (issued May 14, 1985); U.S. Pat. No. 4,988,239 (issued Jan. 29, 1991); and U.S. Pat. No. 5,051,041 (issued Sep. 24, 1991).
Large scale transport and/or metering of certain particulates, such as coal or friable food products, presents unique problems. A transport apparatus or system which is suitable for transporting one type of coal or other friable material may not be suitable for transporting a different type of coal or other friable material. For example, Kentucky coals maintain reasonable integrity when transported through conventional devices such as screw feeders and conveyor belts. However, Western United States coals tend to be more friable and may be degraded to a significant degree during normal transfer operations. It would be desirable to provide an apparatus which is capable of transferring all types of coal or other friable materials with a minimum amount of degradation.
A number of factors must be considered in the design of an efficient device for transporting or metering particulate materials. For example, the amount, size and type of particulate material to be transported must be taken into consideration. The distance over which the material is to be transported and variations in the surrounding pressure during transport must also be taken into account. The water content of the particulate solids is another factor which must be considered. It would be desirable to provide a pump device which is capable of transporting and metering a wide variety of particulate materials under both ambient and pressurized conditions.
The ability of an apparatus to apply drive force to a given type of particulate material is dependent upon a number of factors relating to the design and configuration of the apparatus. The design and configuration of some prior apparatuses makes them unsuited for certain applications requiring a relatively large amount of drive force and/or an efficient transfer of the drive force to the particulate material. For example, in certain applications, it may be necessary to transport a particulate material against a resistance, for example, vertically upward against gravity, up an incline, against a pressure head and/or over a relatively large distance. Therefore, it would be desirable to provide an apparatus and method for transporting and metering a wide variety of particulate materials with an improved ability to apply drive force to the particulate materials.
It is apparent from the above background that there is a present need for a solids handling or pumping device which operates as a single unit to provide simultaneous transport and metering of particulate material with improved drive force. The unit should be capable of transporting and metering a wide variety of particle types under a wide variety of conditions. Further, the unit should be structurally strong, and mechanically simple and durable so that it can be operated continuously over extended periods of time without failure.